1. Field of the Invention
The present invention relates generally to cryospray systems, cryogenic spray ablation and cryosurgery systems, and more particularly, to an advanced cryospray ablation system having consistent cryogen flow and flow control, an integrated suction pump, a body cavity pressure sensor and an assortment of flexible cryogen delivery catheters.
2. Related Art
A variety of medical conditions may be treated by ablation of tissue within the body. Tissue ablation refers to the removal or destruction of tissue, or of tissue functions. Traditionally, invasive surgical procedures were required to perform tissue ablation. These surgical procedures required the cutting and/or destruction of tissue positioned between the exterior of the body and the site where the ablation treatment was conducted, referred to as the treatment site. Such conventional surgical procedures were slow, costly, high risk, and resulted in a long recovery time.
Cryoablation is a relatively new procedure in which tissue ablation is conducted by freezing diseased, damaged or otherwise unwanted tissue (collectively referred to herein as “target tissue”). Appropriate target tissue may include, for example, cancerous or precancerous lesions, tumors (malignant or benign), fibroses and any other healthy or diseased tissue for which cryoablation is desired.
Cryoablation may be performed by using a system that sprays low pressure cryogen on the target tissue. Such systems are often referred to as cryospray systems, cryosurgery spray systems, cryosurgery systems, cryogen spray ablation systems or simply cryospray ablation systems. As used typically, cryogen refers to any fluid (e.g., gas, liquefied gas or other fluid known to one of ordinary skill in the art) that has a sufficiently low boiling point to allow for therapeutically effective cryotherapy and is otherwise suitable for cryogenic surgical procedures. For example, acceptable fluids may have a boiling point below approximately negative (−) 150° C. The cryogen may be nitrogen, as it is readily available. Other fluids such as argon and air may also be used. Additionally, liquid helium, liquid oxygen, liquid nitrous oxide and other cryogens can also be used.
During operation of a cryosurgery system, a clinician, physician, surgeon, technician, or other operator (collectively referred to as “operator” herein), sprays cryogen on the target tissue via a delivery catheter. The spray of cryogen causes the target tissue to freeze or “cyrofrost.” This freezing of the tissue often causes the target tissue to acquire a white color (indicative of cryofrost). The white color indicates that the target tissue freezing has inititated. The physician may visually monitor and/or time additional cryospray duration in order to control the depth of injury. The temperature range for cryofrost can be approximately negative (−) 10° C. to approximately negative (−) 75° C. Alternatively, the temperature range can be from negative (−) 50° C. to (−) 195° C., particularly in the case of liquid nitrogen at low pressure. However, the particular temperature for cryofrost will depend on the target tissue, including size, location, etc. The time period to reach cryofrost may vary, from approximately 5 seconds to approximately 2 minutes or more depending on the size and location of the target tissue and the thermodynamic potential of the cryogen. A cryosurgery system may include a camera system that enables the operator to monitor the cryogen delivery and determine when cyrofost has occurred.